Apparatus for electrical precipitation



Jan. 3, 1939. F. w. Hoss ET AL APPARATUS FOR ELECTRICAL PRECIPITATIONFiled April 19, 1957 n 0000000. 00000000 ooeomvooo 0 n. I 0 0 O U O UPIIIIIIIII/Illlll/ I 71 I .15 I; I91 I71 I .Id I? lilrfffffll H IINYENTORS. m 4/4 ::7-M BY @ozza/ ATTORNEYS Patented Jan. 3, 1939 UNITEDSTATES APPARATUS FOR ELECTRICAL PBEOlPITATION Friedrich Wilhelm HossandWalther Deutscli, Frankfort-on-the-Main, Germany, assignors toInternational Precipitation Company, Los Angeles', CaliL, a corporationoi. California Application April 19, 1937, Serial No. 137,865

Germany April 22, 1936 Claims. (01. 183-7) The present invention'relatesgenerally to' improvements for effecting the electrical precipitation ofsuspended particles from a stream of gas,

and more especially to apparatus for this purpose "5 in which theparticles are. first charged intone field and'then precipitated out in asecond field. In precipitators of this latter type, the gas is firstpassed. through a discharging or ionizing field in which the particlesbecome electrically charged, and then the gas is passed through aseparate substantially non-discharging field in which precipitation ofthe particles takes place on one or more collecting electrodes. Inelectrical precipitators as usually constructed, the gas stream flowspast the electrode surfaces in a direction generally parallel thereto,while the electrical field is maintained between the electrodes and sois more or less at right angles to the gas fiow. This arrangement issat- .20 isfactory for ionizing purposes but in the area ofprecipitation the gas stream oiTers little or no assistance to theseparation of particles from the gas, but rather interferes with theseparation, for there is a tendency to pick up and carry 25 along in thegas stream material that has been previously deposited;

It is a general object of our invention to in-. crease the efficiency ofa precipitatorof the kind described and especially to increase theefiectiveso ness of the precipitation field in bringing about completeseparation of the suspended particles from the gas stream. It is also amain object of our invention to provide a precipitator of the two-fieldtype in 35 which the gas stream and the precipitating field exert theirforces in the same direction on the suspended particles and so reinforceeach other in effecting precipitation oi. the particles.

A further object is to 40 of the two field type in which theprecipitating field has a fiuid-pervious electrode through which gaspasses to bring about intimate contact oi the entire gas. stream withthe electrode and complete precipitation of the suspended particles. 45These objects are attained according to our invention by passing thestream of gas,containing suspended particles previouslycharged'electrically, through a non-discharging precipitation field, andmaintaining the precipitation field in I 50 such a direction that theforce it exerts on the suspended particles generally coincides with thedirection of stream flow and so aids the movement or the particlestoward the collecting electrode.

u One form of apparatus embodying the prinprovide a precipitator ciplesof the invention includes a discharge electrode, an intermediatefiuid-pervious electrode through which gas flows, and a collectingelectrode, which may or may not be fluid-pervious.

.There is also provided means for establishing a 6 high potentialionizing field between the discharge and intermediate electrodes and-asepa-' rate substantially non-discharging field between the intermediateand. collecting electrodes to;

effect precipitation of the charged particles. The' lii' polarity of theintermediate and collecting electrodes relative to each other is suchthat the precipitating field moves the charged particles in the generaldirection of the 'gas flow from the intermediate to the collectingelectrode. 15

How these and other objects and advantages of our invention are attainedwill be better understood by reference to the following description .andthe annexed drawing, in which:

Fig. 1 is a vertical section through a preferred form of precipitator,illustrated somewhat diagrammatically, with suitable electricalequipment also indicated diagrammatically;

Fig. 2 is a horizontal section on line 2-2 01' Fig.1; i

Fig- 3 is a fragmentary vertical section through a variational form ofprecipitator; and

Fig. 4 is a horizontal section upon line 4-4 in Fig. 3.

The form of precipitator illustrated in Figs. 1 and 2 comprises anexternal housing III which is preferably circular in cross-section andis provided with a trap door l2 at the bottom through which precipitatedmaterial can be periodically removed. The-housing i0, which serves asa001- lecting electrode, is of sufiiciently extended surface andsmallsurface curvature to substantially preclude corona 'dischargetherefrom. Fluidpervious intermediate electrode i4 is placed within andconcentrically of the housing and is sup.- 40 ported upon insulators l5which electrically insulate the electrode from the housing. Electrode i4is shown as made of perforated plate, butit may be made of wire screenor any other similar material that allows free passage of the gasthrough the electrode and is of sufilciently extended surface and lowsurface curvature to substantially preclude corona discharge therefrom.Intermediate'electrode i4 is closed at its upper end by plate It whichalso serves as a support for insulator l8 by'means of which dischargeelectrode 20 is mounted axially of the intermediate electrode. Thedischarge electrode is a wire or'small diameter rod and is provided atits lower end with tensioning means, such as weight II.

Gas is introduced into the precipitator through inlet pipe 24 whichdischarges upwardly from nozzle 25 into the lower end of intermediateelectrode 14., The gas passes through the openings in the intermediateelectrode and is discharged from the precipitator through the open upperend 26 of housing Ill. Although the lower end of electrode l4 may beclosed by means of a nonconducting member, which will insulate theelectrode from gas nozzle 25, this 'is not necessary with theconstruction illustrated. The gas, issuing from nozzle at a relativelyhigh velocity, is

projected into the upper portion of the electrode, and by constrictingthe open lower end of the electrode around nozzle 25, substantially nogas escapes from the electrode at this point.

The electrical equipment may be varied as desired to suit operatingrequirements. As typical of a preferred arrangement, but withoutlimitation thereto, we show means for supplying the precipitator withrectified high tension alternating current. After the alternatingcurrent is stepped up by transformer 30, it is passed through a fullwave rectifier 3! so that unidirectional current is supplied todischarge electrode 20 by leads 32 and 33. A voltage divider 34 isincluded in the circuit so that current at a lower voltage may besupplied to intermediate electrode l4 by lead 35. It will be realizedthat there may be employed a separate source of electric power for eachof the discharge and intermediate electrodes, instead of the singlesource shown.

Housing i0 is connected with the ground at 38 so that, with respect toit, electrodes i4 and 20 are both of the same polarity. The potentialapplied to discharge electrode 20 is sufficiently great' to produce thewell known corona or silent discharge from it, but not sufiicient tobring about a disruptive or spark discharge. A lesser potential isapplied to electrode [4 than that applied to the discharge electrodeand, electrode I4 being without sharp corners or projections of smallradius which would promote the formation of corona discharge, there ismaintained'in the annular space between electrode l4 and housi'ng In asubstantially non-discharging electri-- cal field. It is preferred, butnot necessary, that discharge electrode 20 be charged negatively andconsequently electrode I4 is also negative with respect to housing Illbut is positive with respect to the discharge electrode.

The gas issuing from nozzle 25 first reaches the discharge electrode andtravels' parallel to it, bringing the suspended particles into theionizing field where they become charged negatively, that is of the.same polarity as the charge of electrode 20. The fiow of gas is thenradially outward through the openings in electrode l4 and the chargedparticles, being repelled by electrode 20, are moved by the electricfield in the same directicn. The gas and suspended particles afterpassing through fiuid-pervious electrode l4, enter the precipitatingfield maintained in the annular' space around electrode l4. The chargedparticles are then in a strong field of such polarity that they arerepelled by electrode II, the direction of the field moving them towardhousing Ill which acts as a collecting eleotrode upon' which theparticles are precipitated when'they come in contact therewith and losetheir charge.

' Thedlrection of gas movement through the intermediate fiuid-perviouselectrode is radially-outward in the same direction as the movement ofwhich is grounded at 36.

that the gas movement and the field reinforce each other. Thus both theionizing and precipitation fields are of a polarity to reinforce the gasstream in moving suspended particles. The cleaned gas is then deflectedupwardly and dischargedfrom the open upper end of housing It. mFigs. 3and 4 disclose a variational form of precipitator in which thedischarge, intermediate and collecting electrodes are mounted in planesacross 'flue 40, typically rectangular in crosssection. The dischargeelectrodes 20a are mounted in a rectangular frame 4| supported from thetop of the flue on insulators 42. Fluidpervious intermediate electrode ais likewise mounted on a rectangular frame and supported from insulators43. Insulators 42 and 43 electrically insulate the discharge andintermediate electrodes from each other and .from fiue' 40 Collectingelectrode 45, herein shown as a fiuid-pervious member made of wirescreen or the like, is supported directly from the flue walls and iselectrically connected therewith. The electrical connections 33 and 35are the same as described in Fig. 1 and respectively supply high tensionunidirectional current to the discharge and intermediate electrodes.

The electrodes are so arranged that the gas stream moving toward theright, as indicated by the arrow in Fig. 3, will encounter successivelyelectrodes 20a and Na, in which field the particles suspended in the gasbecome charged electrically with the same polarity as the dischargeelectrodes. The gas stream with its charged particles then moves throughthe fiuid-pervious intermediate electrode I40 and enters thenondicharging field maintained between electrodes "a and 45, in whichthe polarity of the electrodesis such that the suspended particles aremoved in the direction .of stream flow toward the collecting electrode45. It will be noted that the mode of operation and electrodearrangement are the same as described in connection with Fig. 1, exceptthat in the present form both the intermediate and collecting electrodesare fluid-pervious.

Apparatus in which the ionizing field is spaced from the precipitatingfield by a substantial distance, asby replacing the intermediateelectrode by twoindividual electrodes so that the ionizing field ismaintained between one pair of electrodes and the precipitating fieldbetween a separate second pair, is described and claimed in ourcopending application Serial No. 137,864, filed April 19, 1937, whichapplication also broadly claims the apparatus and the method ofoperation embodied in both applications. Since various changes in theshape, arrangement and application of the various parts of our inventionmay be made without departing from its true spirit and scope, thedescription and drawing are to be construed as illustrative of ratherthan restrictive upon the appended claims.

We claim:

1. In an electrical precipitation apparatus through which flows a streamof gas containing suspended particles to be removed, the combina- 4 tionof a discharge electrode; an intermediate 75 particles induced by theprecipitating iield. so and a separa e tially non-discharging The gasfirst passes ,through an ionizing ,field maintained betweenprecipitating field between the, intermediate and collecting electrodes,the precipitating field being of such direction as to reinforce gas flowfrom the intermediate to the collecting electrode for' collectionthereon of suspended particles.

2. In an electrical precipitation apparatus through which flows a streamof gas containing suspended particles to be removed, the combination oiadischarge electrode; an intermediate fiuid-pervious electrode throughwhich gas flows; a collecting electrode; said three electrodes beingarranged successively in the path of gas flow; and means forestablishing an ionizing field between the discharge andintermediateelectrodes, and a separate substantially non-dischargingprecipitating field between the intermediate and collecting electrodes,the polarity of the discharge and intermediate electrodes being thesame, relative to the collecting electrode, with a potential lectingelectrodes, the precipitating field being of such direction as toreiniorcegas fiow from the intermediate to the collecting electrode iorcollection thereon of suspended particles.

' arcane I 4. In an electrical precipitation apparatus through whichflows a stream of gas containing suspended particles to be removed, thecombination of a discharge electrode; a hollow intermediatefiuid-pervious electrode through which gas flows, surrounding thedischarge electrode; a hollow collecting electrode surrounding theintermediate electrode; said three electrodes being arrangedsuccessively in, the path of gas flow; and means for establishing anionizing field between the discharge and intermediate electrodes, and aseparate, substantially non-discharging precipitating field between theintermediate and collecting electrodes, the precipitating field beingofsuch direction 'as tolreinforce gas flow from the intermediate to thecollecting electrode for collection thereon of suspended particles.

5.- In an electrical precipitation apparatus through which flows astreamof gas containing suspended particles to be removed, thecombination of a discharge electrode; an intermediate fluid-perviouselectrode through which gas flows; a collecting electrode said threeelectrodes being arranged successively in the path oi gas fiow; andmeans for establishing an ionizing field between the discharge andintermediate electrode, and a separate substantially non-dischargingprecipitating field between the intermediate and collecting electrodes,both the ionizing and the precipitation fields being of such polarity asto move particles in the same direction to reinforce gas flow throughthe intermediate pervious electrode.

FRIEDRICH WILHELM H088. WALT-HER DEUTSCH.

